Conventional mechanical seal assemblies are employed in a wide variety of environments and settings, such as for example in mechanical apparatuses, to provide a fluid-tight seal. The sealing assemblies are usually positioned about a rotating shaft or rod that is mounted in and protrudes from a stationary mechanical housing. The rotary seal is generally constructed and designed so as to try to prevent unwanted particles from entering the machine housing and contaminating a fluid contained therein, but the seal must also retain fluid, such as oil, process fluid or a barrier fluid, typically located in a fluid reservoir inside the housing. Hence, the need for minimizing leakage while prolonging the machine's operating life is important, as the demands for reliability and the penalties for failure continue to rise.
Those of ordinary skill in the art will readily recognize that it is typically difficult to maintain rotating equipment because of extreme equipment duty cycles, the lessening of service factors, the particular seal design, and the lack of spare rotating equipment in many processing plants. Various forms of conventional shaft sealing devices have been utilized in the art to try to protect the integrity of the seal environment, including lip seals, labyrinth seals, magnetic seals, and the like.
Conventional lip seals include a sealing element with a lip that helps prevent leakage of fluid from the housing by contacting the rotating shaft. A drawback of conventional lip seals is that they can quickly wear out and fail over time, and are also known to permit excessive amounts of moisture and other contaminants to migrate into the fluid reservoir of the housing.
A labyrinth seal is typically a non-contacting frictionless seal that includes no friction, given that there is no sealing contact between the stationary component and the revolving component during use. The labyrinth seal is capable of creating a seal and preventing contaminants from reaching the fluid within the housing by creating a complicated path (i.e., a labyrinth) for liquids to pass through, thus making it challenging for liquids to cross the barrier created by the seal because they have difficulty making their way through the labyrinth. These types of seals are used in a variety of settings, and can be used on objects which rotate and otherwise move. Indeed, movement such as shaft rotation can often make the labyrinth seal even more effective, depending on the design, by creating a centrifugal force that further serves to trap contaminants and fluids within the seal. While a labyrinth seal is typically not designed to handle pressure differentials, it can be used in many other types of important environments.
A drawback of conventional labyrinth seals is that that they are expensive and typically have complex designs that require tight tolerances. Any movement of the parts of the seal from their default positions during operation results in increased fluid leakage and a reduction in the ability of the seal to prevent contaminants from entering the mechanical housing.